Is there anything on the blackberry that helps it to learn how you speak to make voice dialing more accurate? I used to have a phone that you could run a progam that asked you to speak certain words so that is was more accurate. I can't remember if it was my old samsung or LG.
If you go to your Options, Voice Dialing, then click your Menu key, you can choose Adapt Digits. This walks you through a series of quick voice tests to help improve the accuracy. Make sure you're someplace quiet when you try.